Diaphragm for telephone receivers



Ap ril 21, 1925;

H. FISCHER DIAPHRAGM FOR TELEPHONE RECEIVERS Filed Oct. 25 ,1922

INsKENTOR y /W AM/ ATTORNEYS Patented Apr. 21:, 1925..

, UNITED STATES hdfidfill PATENT -Fl lfilli HERMANN FISCHER, OF NEW YORK, N. Y., ASSIGNOR TO C. "BRANLDES, INEL, A CDRPQBA- T1011 01 NEW YORK.

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Application filed oototer 25, 1922. Serial No. 596,741.

To all whom it may concern:

Be it known that I, Hermann FISCHER, a citizen of Russia, residing at New York, in the county of New York, State of New York, have invented certain new and useful Irn rovements in Diaphragms for Telephone eceivers; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to sound producing diaphragms and more particularly to diaphragms for use in telephone receivers.

The object of the invention is to efiect an improvement in telephone receivers-by increasing the volume of sound production for a given amount of input energy. In other Words, the object is to increase the efficiency of telephone receivers.

As a result of extensive experimental work it has been found that a telephone receiver provided with two sulperposed or superimposed d-iaphragms wi 1, under proper conditions, reproduce signals with substantially increased volume. The conditions apparently essential for the best results arefirst, that the outer diaphragm, that is the diaphragm farthest from the magnet poles, should be perforated; second, that the diaphragins should be out of contact with each other at their center portions; and third, that they should be tightly clamped together at their peripheries. The first of these conditions is the only one which is absolutely vital to the attainment of improved response in accordance with the invention, while the last two conditions named are merely contributoryto further improved response. It should not be presumed, however, that the last two conditions are immaterial. They are in fact quite. vital, although relatively-less vital than the first.

Theinvention, therefore, consists broadly in the combination. of two superimposed or superposed diaphragms in which one only of the diaphragms is perforated. More specifically it consists of the aforementioned combination modified in. that the two diaphragnis are out of contact at their center portions, and still more specifically in that the two diaphragrns are in intimate contact at their peripheral portions forming an air chamber having a column of air therein of a substantial depth.

lit has been found that the outer dia phragm may be perforated in many difier out ways with varying degrees of improvement resulting. Some of the very best results, however, have been obtained with LII outer diaphragm provided with a so-called f-hole or with a pair of crossed f-holes at the .center portion thereof. The f-holes referred to are'so called on account of their v similarity in form to the f-holes of a violin and it is thought that the improved response resulting from their use is due to reasons somewhat akin to the reasons for their use in violins.

In my copending application'Serial No. 596,629 filed October 24, 1922, there is dis closed a telephone diaphragm rovided with an f-hole at its center portion. As pointed out therein, the improvement resulting from. the provision of an -hole or its equivalent as distinguished roin other forms of apertures is that the lower notes of the musical scale are reproduced in more correct proportionate volume with respect to the higher notes than is the case with plain diaphragms such as are ordinarily used in telephone receivers. The reason for the improved response of a diaphragm pro-- vided with an f-hole is not definitely known, but the most plausible explanation which has been advanced is that the rojecting portions of the diaphragm, w ich are defined by the f-hole, have a lower natural frequency than the diaphragm as a whole, and that they therefore respond to magnetic flux variations of lower frequencies with greater amplitude than the diaphragm as a whole, accordingly accentuatingthe lower notes which are ordinarily greatly attenuated.

The difference in resultant volume of respouse between the diaphragm provided with a single f-hole and one provided with a pair of crossed f-holes is very slight but the cumulative results of many tests indicate a slight advantage in favor of the latfor. The preferred form of the invention, therefore, includes an outer diaphragm having a pair of crossed f-holes at its center portion. p

No really plausible and reliable explanation of the operation of the present invention has yet been deduced, an for that rea son no such explanation will be undertaken herein. Ample iniormation, however, is

no i

7 ng which ifo' i'cation, l is cross'sc' '4 e. wotchcose type double nole oeiver having o pun.- oi supe phragms in accordance with he I 2 is a piun view of u disphrog; n huving; an f-hole at its center portion; and

Fig. 3 e plan view xt it dicph gm having a pair of crosi. I Fholcs at its center POTQOIL The receiver shm" l is, general, -c convc-n local i pole type compr :icasing l in which mounted a permanent magnet 2 having pair oi? polcpieces S, 3 which form cores for the windings i, and threaded cup 5,

In addition, however, to the plain diunhragm G, which. is o' no usual type, there is 7I'OVid2d J. oin. gm. which is perforated pro" hi as shi an. in either of Figs, 2 or 3. .L phmgui (i normally somewhat dished its center PO'liliOll by reason of the in-it etic attraction the-pole pieces 3, 3 Whicn are permanently magnetized, and the diaphragm 7 is ihigic oi" though not necessariiy, slightly d in the opposite direction that v.1

viewed in Fig. The dishing i the upper to insure a: dclinite separaof the lion 1t nose, the dimension fl. of the j -hole up proximately 1- niension B was approximotely 52 K dini s oporoximetely .010, and ti 1 together 2 may admins i y pi i together by soidorino, hruzo. otherwise.

The increased response resulting "from this invention of such extent to be distinctly apparent oven to inexperienced persons.

It is not (iesired that the invention be con-- embodiment oppendi'ucd as limited to the specific only by tne st c mud producing instrumentelity,

l (iitlphlilglllS each con o "her at their respective and forming in air cimm i her-oi ct'uecn, at least one of solid, oinplnngnis loving u narrow sport c therein cxiending substantially along a diameter of said diupliruqm, and DE ans for actuating at least one 01 said ationlnugnis for prodncing sound vihri ions.

'2. in :1 sound producing instrumentality, a pair 0 superimposed disphrugrms ouch con touting with the other at their respective peripheries and forming on air column there between at least one of said diuphrugms nuring un shaped slot therein, and moons for actuating at least one of said diuphragins for producing sound. VJ one.

3. in s sound producing instrumentality, a pair of supewoscd dinphraglns each contacting with the cl peripl'ierics, E1} 1st one of said diaphragms having; :1 dinn'letricuily cxtendin slot therein said diiiphrugnis jointly defining a chamber between their adjacent surfaces, and means for actuating at least one of said diaphragins i'or producing sound vibrations.

in a sound produc a pair of superimposed one of said diaijln'sgnis positioned narrow slot having :1 centrally therein, said diaportions to enclose an air column, and means for actuating at least one of said din-- phrugms for producingsound vibrations.

u a sound producing instrumentality, a pair of superimposed diuphrugms, at least one of said diupiirzp being dished at its center portion so as to form, conjointly with the other of said dinphragms, a chamber enclosing on air column therehct-ween, lealst one oi' said dinphru us being perforated "with :i narrow (liurneti .cslly positioned slot ntin at least one of sai ihrutions.

1e other and dished center portion so s to form, conjoin'tly 5 id other diaphragm, a chamber there u e L ian'iragrni being perforated by means of on f shupel aperture for preventing interference between vibrating" portions of said diephragms, and means for actuating the thinner one of said. disphmgins for producing sound vibrations.

7. In it sound producing instrumentality, a pair of superposed diuphragms, one oi? at their respective enclosing; on air column, said dished 4 for producing sound vibrations. 15

29 dished at its center portion so as to form,

said diaphragms being provided .ith an f hole at its center portion, and iiieans for actuating the other of said diaphragms for producing sound vibrations.

8. In a soundprcducing instrumentality', a pair of superimposed dia'phragms having their respective peripheries in contact with each other, one of said diaphragms being provided with an f-hole and dished at its center portion so as to form, conjointly with the other of said diaphragms, a chamber therebetween enclosing an air column, and means for actuating one of said diaphragms 9. In a sound producing instrumentality, a pair of superimposed diaphragms having their respective peripheries in contact with each other, one of said diaphragms bein provided with a pair of crossed f-holes and conjointly with the other of said diaphragms, a chamber therebetween enclosing an air column, and means for actuating one of said diaphragms for producing sound vibrations.

l0. In a -telephone receiver, a pair of superimposed diaphragms having their respective peripheries clamped together, one of said diaphragms being substantially thicker than the other, said thicker dia phragm being perforated atits center portion and dished, the concave side of said thicker diaphragm being adjacent the thinner one of 'said diaphragms, thereby forming a=chamber therebetween enclosing an air column, and ankelectromagnet for actuating the thinner diaphragm-for producing sound vibrations. V

y In testimony whereof I aiiix my signature.

HERMANN FISCHER. 

